POWER ELECTRONICS – PAGE 14
Full Wave Controlled Rectifier with R-L Load
1️⃣ Why R-L Load is Different?
In R-load, current follows voltage immediately. But in R-L load, inductor stores energy → current continues even after supply crosses zero.
Current does NOT become zero at π.
2️⃣ Conduction Period
- SCR triggered at firing angle α
- Current continues beyond π
- Conduction stops at extinction angle β
Conduction interval = α → β
Where:
- β > π
- β depends on L value
3️⃣ Output Voltage
During conduction:
v = Vm sin θ
After β:
Output voltage becomes zero.
4️⃣ Average Output Voltage
For R-L load:
Vavg = (1 / 2π) ∫αβ Vm sinθ dθ
After integration:
Vavg = (Vm / 2π) (cos α − cos β)
5️⃣ Important Observations
- Current waveform becomes smoother
- Conduction extends beyond π
- Output may become negative for certain α
- Power factor reduces
6️⃣ GATE / PSU Focus
- Understand extinction angle β
- Difference between R and R-L load
- Waveform identification
- Integration limits change
Very Important: If β = π → behaves like R-load. If β > π → inductive effect dominant.
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